As a temperature sensor for detecting the temperature of exhaust gas in an automotive engine, for example, Patent Documents 1 to 5 disclose related temperature sensors.
FIGS. 6A to 6C are sectional views showing the configuration of a related temperature sensor, focusing on a metal tube 512. As shown in FIG. 6A, a temperature sensor 500 includes a thermistor element 502 that has a thermistor sintered body 503 and an element electrode wire 504, and a sheath member 506 that holds a sheath core wire 508 in a sheath pipe 507 in a state where electrical insulation is provided between the sheath pipe 507 and the sheath core wire 508. The element electrode wire 504 extending from the thermistor sintered body 503 is laser spot-welded to the sheath core wire 508 which extends from a front end of the sheath pipe 507. The thermistor element 502 and the sheath core wire 508 connected to the element electrode wire 504 are accommodated in the metal tube 512 made of a stainless alloy. Insulating cement 514 made of thermally resistant oxide (Al2O3 [alumina] or the like) is filled in the internal space of the metal tube 512 to function as a holding member for suppressing shaking of the thermistor element 502 due to vibration.
The temperature of exhaust gas may vary over a wide range from a low temperature of −40° C. to a high temperature of 1000° C. For this reason, the temperature sensor 500 may be used to detect temperature in such a wide temperature range. Accordingly, the temperature sensor 500 is exposed to the environment of a cooling/heating cycle at low/high temperature.    [Patent Document 1] JP-A-2005-55254    [Patent Document 2] JP-A-2004-301679    [Patent Document 3] JP-A-2000-266609    [Patent Document 4] JP-A-2000-234962    [Patent Document 5] JP-A-2007-170952